1. Field of the Invention
The invention resides in the field of adjustable workpiece mounting stages and more particularly relates to a modification in the mounting table to which the work pieces are attached to compensate for minor deviations in component fabrication and stage assembly.
2. Description of the Prior Art
Precision positioning stages of the type relating to the invention are disclosed in U.S. Pat. Nos. 4,652,095 and 5,077,620 issued to the applicant. In the first of these, the device described employs an adhesive assembly concept for a stage utilizing two end plates having grooves for receiving a pair of parallel smooth cylindrical rails and a mounting table slidably disposed between the plates.
In the second of these, which is an improvement of the first, there is disclosed an electrical motor, gear system, and encoder mounted on an additional plate also disposed between the rails, the motor being operationally connected to the mounting table by a threaded rod such that the table is moved by actuation of the motor.
In the manufacture and construction of these precision devices, great care must be taken in fabricating the component parts and assembling them into a finished unit. Tolerances must be within one or two thousands of an inch for both fabrication and assembly in order to achieve a unit which will function properly over a period of time. It has been found that even the most rigorous shop standards will not prevent the failure of a percentage of units which is greater than desirable. Further, additional units which function well upon delivery will, over a period of time, wear to the point of unacceptable performance. The present invention is intended to alleviate the above mentioned problems in the interaction of the two main components of these stages, i.e. the rails and the mounting table which moves between them. This is accomplished by a modification to the mounting table providing a take-up mechanism to compensate for minor deviations in component fabrication and assembly.